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https://sussex.ac.uk

Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
77
GRADE
C
FIX
3
REVIEW
3
PASS
7
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
68
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
96
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

2.08 s

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

3.17 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

0 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.001

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

2.90 s

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

3.17 s

Page Load Progression

688 ms
1.4 s
2.1 s
2.8 s
3.4 s
4.1 s
4.8 s
5.5 s
Checks
15
7 PASS 3 REVIEW 3 FIX
F
Page Weight Budget
Action
3.3 MB transferred, 65 requests
FIX
3.3 MB transferred, 65 requests
Warning::
Page weighs 5.1 MB (3.3 MB transferred)
Info::
Fonts are 2.0 MB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 2.0 MB
Info::
65 HTTP requests
Info::
Estimated 0.70 g CO2 per page load
3.3 MB / 2.4 MB budget
3.3 MB transferred
65 requests
0.70 g CO2 per page load
Fonts 2.0 MiB 59%
Images 881.7 KiB 26%
JavaScript 409.9 KiB 12%
CSS 81.6 KiB 2%
HTML 19.7 KiB 1%
Other 3.3 KiB 0%
Other 455 B 0%
Other 142 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over budget

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (3.3 MiB of 3.3 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
Page Weight Inventory
Action
65 resources · 3.3 MB · 26 KB savings available
FIX
65 resources · 3.3 MB · 26 KB savings available
Warning::
Page weight 2.3 MB over 1MB target
Got: 3.3 MB Expected: ≤ 1 MB
Warning::
64 third-party resources (100% of weight)
Info::
4 resources over 200KB
65 resources · 3.3 MiB · 64 third-party 2.3 MiB over 1MB target
Font 59% · 2.0 MiB
Image 26% · 884.6 KiB
JavaScript 12% · 409.9 KiB
CSS 2% · 81.6 KiB
Document 1% · 20.1 KiB
Other 0% · 597 B

~25.6 KiB of savings available

Remove unused JavaScript: 25.6 KiB
C
Image Optimization
Action
41 images, 0 KB saveable
REVIEW
41 images, 0 KB saveable
Warning::
https://www.sussex.ac.uk/assets/images/homepage/la... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/ai... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/ne... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/ne... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/st... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/de... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/ne... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/dh... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/ea... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/re... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.sussex.ac.uk/assets/images/homepage/vi... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
41 images 882 KB
0 oversized -0 KB
19 legacy format
11 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

B
JS Execution Cost
530ms total JS execution
REVIEW
530ms total JS execution
Warning::
https://www.sussex.ac.uk/: 355ms CPU time
Info::
Unattributable: 175ms CPU time
Warning::
Third-party scripts: 530ms (100% of total)

Main Thread Breakdown

Style & Layout 38% Other 38% Script Evaluation 11% Rendering 8%
ScriptTotalScriptingParse/CompileParty
https://www.sussex.ac.uk/355ms1ms0ms3rd
Unattributable175ms2ms0ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
Font Loading
4 fonts (2026 KB)
PASS
4 fonts (2026 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

2026 KB total

Render-blocking

0

of 4

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 2.1 s LCP 3.2 shttps://www.sussex.ac.uk/assets/fonts/Inter-VariableFont_opsz,wght.ttfInter-VariableFont_opsz... https://www.sussex.ac.uk/assets/fonts/Inter-VariableFont_opsz,wght.ttf — 854.6 KiB — 3.8 s — font-display: swaphttps://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Regular.ttfLibreBaskerville-Regula... https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Regular.ttf — 144.5 KiB — 1.2 s — font-display: swaphttps://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Bold.ttfLibreBaskerville-Bold.ttf https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Bold.ttf — 143.3 KiB — 1.2 s — font-display: swaphttps://www.sussex.ac.uk/assets/fonts/Inter-Italic-VariableFont_opsz,wght.ttfInter-Italic-VariableFo... https://www.sussex.ac.uk/assets/fonts/Inter-Italic-VariableFont_opsz,wght.ttf — 883.7 KiB — 1.0 s — font-display: swap
Inter-VariableFont_opsz... ttf swap
Size 855 KB
Load time 3.8 s
Start 1.6 s
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
LibreBaskerville-Regula... ttf swap
Size 145 KB
Load time 1.2 s
Start 1.6 s
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
LibreBaskerville-Bold.ttf ttf swap
Size 143 KB
Load time 1.2 s
Start 1.6 s
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
Inter-Italic-VariableFo... ttf swap
Size 884 KB
Load time 1.0 s
Start 2.2 s
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
Optimization checklist
  • Preload critical fonts (priority=high)
  • Use woff2 format for all fonts
  • Set font-display to swap, optional, or fallback
  • Subset large fonts (≤100 KB each)

Fixing the unchecked items could save ~1621 KB and ~3242 ms

A+
JS Bundles
8 scripts, 26 KB unused
PASS
8 scripts, 26 KB unused
Warning::
https://www.sussex.ac.uk/assets/js/cyclone.js: 26 KB unused (57%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 26 KB
26 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.sussex.ac.uk/assets/js/cyclone.js45 KB26 KB (57%)✓3rd
https://www.sussex.ac.uk/assets/js/libs/jquery/jquery-3.6.0.min.js31 KB—✓3rd
https://f.vimeocdn.com/p/4.46.43/js/player.module.js211 KB—✓3rd
https://f.vimeocdn.com/p/4.46.43/js/vendor.module.js93 KB—✓3rd
https://f.vimeocdn.com/js_opt/modules/utils/vuid.min.js1 KB—✓3rd
https://www.gstatic.com/cv/js/sender/v1/cast_sender.js?loadCastFramework=12 KB—✓3rd
https://www.gstatic.com/cast/sdk/libs/sender/1.0/cast_framework.js12 KB—✓3rd
https://www.gstatic.com/eureka/clank/146/cast_sender.js13 KB—✓3rd

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A
HTTP Caching
max-age=300 (5 minutes)
PASS
max-age=300 (5 minutes)
Info::
Cache-Control header is set
Got: max-age=300
Info::
Effective TTL: 5 minutes (max-age=300)
Info::
No ETag or Last-Modified header
Conditional requests (304 Not Modified) are not possible without validators.
Cache-Control

max-age=300

DirectiveValueMeaning
max-age300Cache for 5 minutes
Effective TTL: 300 seconds
Network Waterfall
65 requests over 5616ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 2.1 s LCP 3.2 shttps://sussex.ac.uk// https://sussex.ac.uk/ — 301 — 361 B — 855 ms — http/1.1https://www.sussex.ac.uk/www.sussex.ac.uk/ https://www.sussex.ac.uk/ — 200 — 8.6 KiB — 765 ms — http/1.1https://www.sussex.ac.uk/assets/css/algae.csswww.sussex.ac.uk/assets/css/algae.c... https://www.sussex.ac.uk/assets/css/algae.css — 200 — 57.7 KiB — 442 ms — http/1.1https://www.sussex.ac.uk/assets/fonts/Inter-VariableFont_opsz,wght.ttfwww.sussex.ac.uk/assets/fonts/Inter... https://www.sussex.ac.uk/assets/fonts/Inter-VariableFont_opsz,wght.ttf — 200 — 854.6 KiB — 3.8 s — http/1.1https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Regular.ttfwww.sussex.ac.uk/assets/fonts/Libre... https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Regular.ttf — 200 — 144.5 KiB — 1.2 s — http/1.1https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Bold.ttfwww.sussex.ac.uk/assets/fonts/Libre... https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Bold.ttf — 200 — 143.3 KiB — 1.2 s — http/1.1https://www.sussex.ac.uk/assets/images/homepage/life-at-sussex.jpgwww.sussex.ac.uk/assets/images/home... https://www.sussex.ac.uk/assets/images/homepage/life-at-sussex.jpg — 200 — 21.7 KiB — 610 ms — http/1.1https://www.sussex.ac.uk/assets/images/homepage/masters-event.jpgwww.sussex.ac.uk/assets/images/home... https://www.sussex.ac.uk/assets/images/homepage/masters-event.jpg — 200 — 43.4 KiB — 602 ms — http/1.1https://www.sussex.ac.uk/assets/js/libs/jquery/jquery-3.6.0.min.jswww.sussex.ac.uk/assets/js/libs/jqu... https://www.sussex.ac.uk/assets/js/libs/jquery/jquery-3.6.0.min.js — 200 — 30.6 KiB — 596 ms — http/1.1https://player.vimeo.com/video/222526644?h=34e6e99d8dplayer.vimeo.com/video/222526644?h=... https://player.vimeo.com/video/222526644?h=34e6e99d8d — 200 — 11.1 KiB — 195 ms — http/1.1https://f.vimeocdn.com/p/4.46.43/js/player.module.jsf.vimeocdn.com/p/4.46.43/js/player.... https://f.vimeocdn.com/p/4.46.43/js/player.module.js — 200 — 211.3 KiB — 38 ms — h2https://f.vimeocdn.com/p/4.46.43/js/vendor.module.jsf.vimeocdn.com/p/4.46.43/js/vendor.... https://f.vimeocdn.com/p/4.46.43/js/vendor.module.js — 200 — 93.5 KiB — 34 ms — h2https://f.vimeocdn.com/p/4.46.43/css/player.cssf.vimeocdn.com/p/4.46.43/css/player... https://f.vimeocdn.com/p/4.46.43/css/player.css — 200 — 23.9 KiB — 24 ms — h2https://i.vimeocdn.com/video/2116207332-465dd8421f362ccd5688d7fc827410bea2e02217ce65f540a5f15f03397e921b-d?mw=80&q=85i.vimeocdn.com/video/2116207332-465... https://i.vimeocdn.com/video/2116207332-465dd8421f362ccd5688d7fc827410bea2e02217ce65f540a5f15f03397e921b-d?mw=80&q=85 — 200 — 1.2 KiB — 13 ms — h2data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' viewBox='0 -…www.w3.org/2000/svg' height='24' vi... data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' viewBox='0 -… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 24 24' fill='none' xmlns='http://www.w3.org/20…www.w3.org/20… data:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 24 24' fill='none' xmlns='http://www.w3.org/20… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' width='24' f…www.w3.org/2000/svg' height='24' wi... data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' width='24' f… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' width='24'%3…www.w3.org/2000/svg' height='24' wi... data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' width='24'%3… — 200 — 0 B — 1 ms — datahttps://f.vimeocdn.com/js_opt/modules/utils/vuid.min.jsf.vimeocdn.com/js_opt/modules/utils... https://f.vimeocdn.com/js_opt/modules/utils/vuid.min.js — 200 — 1.1 KiB — 5 ms — h2data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' width='24'%3…www.w3.org/2000/svg' height='24' wi... data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' height='24' width='24'%3… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 18 18' xmlns='http://www.w3.org/2000/svg'%3E%3…www.w3.org/2000/svg'%3E%3… data:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 18 18' xmlns='http://www.w3.org/2000/svg'%3E%3… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 18 18' xmlns='http://www.w3.org/2000/svg'%3E%3…www.w3.org/2000/svg'%3E%3… data:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 18 18' xmlns='http://www.w3.org/2000/svg'%3E%3… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 20 16' xmlns='http://www.w3.org/2000/svg'%3E%3…www.w3.org/2000/svg'%3E%3… data:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 20 16' xmlns='http://www.w3.org/2000/svg'%3E%3… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 18 16' xmlns='http://www.w3.org/2000/svg'%3E%3…www.w3.org/2000/svg'%3E%3… data:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 18 16' xmlns='http://www.w3.org/2000/svg'%3E%3… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' xml:space='preserve' sty…www.w3.org/2000/svg' xml:space='pre... data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' xml:space='preserve' sty… — 200 — 0 B — 0 ms — datahttps://i.vimeocdn.com/video/2116207332-465dd8421f362ccd5688d7fc827410bea2e02217ce65f540a5f15f03397e921b-di.vimeocdn.com/video/2116207332-465... https://i.vimeocdn.com/video/2116207332-465dd8421f362ccd5688d7fc827410bea2e02217ce65f540a5f15f03397e921b-d — 200 — 98.2 KiB — 9 ms — h2data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' xml:space='preserve' sty…www.w3.org/2000/svg' xml:space='pre... data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' xml:space='preserve' sty… — 200 — 0 B — 0 ms — datahttps://www.gstatic.com/cv/js/sender/v1/cast_sender.js?loadCastFramework=1www.gstatic.com/cv/js/sender/v1/cas... https://www.gstatic.com/cv/js/sender/v1/cast_sender.js?loadCastFramework=1 — 200 — 2.5 KiB — 74 ms — h2data:image/svg+xml;utf8,<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://w…w… data:image/svg+xml;utf8,<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://w… — 200 — 0 B — 0 ms — datadata:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 30 24' fill='none' xmlns='http://www.w3.org/20…www.w3.org/20… data:image/svg+xml;charset=utf-8,%3Csvg viewBox='0 0 30 24' fill='none' xmlns='http://www.w3.org/20… — 200 — 0 B — 0 ms — data
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 2.1 s LCP 3.2 shttps://sussex.ac.uk// https://sussex.ac.uk/ — 301 — 361 B — 855 ms — http/1.1https://www.sussex.ac.uk/www.sussex.ac.uk/ https://www.sussex.ac.uk/ — 200 — 8.6 KiB — 765 ms — http/1.1https://www.sussex.ac.uk/assets/css/algae.csswww.sussex.ac.uk/assets/css/algae.c... https://www.sussex.ac.uk/assets/css/algae.css — 200 — 57.7 KiB — 442 ms — http/1.1https://www.sussex.ac.uk/assets/fonts/Inter-VariableFont_opsz,wght.ttfwww.sussex.ac.uk/assets/fonts/Inter... https://www.sussex.ac.uk/assets/fonts/Inter-VariableFont_opsz,wght.ttf — 200 — 854.6 KiB — 3.8 s — http/1.1https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Regular.ttfwww.sussex.ac.uk/assets/fonts/Libre... https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Regular.ttf — 200 — 144.5 KiB — 1.2 s — http/1.1https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Bold.ttfwww.sussex.ac.uk/assets/fonts/Libre... https://www.sussex.ac.uk/assets/fonts/LibreBaskerville-Bold.ttf — 200 — 143.3 KiB — 1.2 s — http/1.1https://www.sussex.ac.uk/assets/images/homepage/life-at-sussex.jpgwww.sussex.ac.uk/assets/images/home... https://www.sussex.ac.uk/assets/images/homepage/life-at-sussex.jpg — 200 — 21.7 KiB — 610 ms — http/1.1https://www.sussex.ac.uk/assets/images/homepage/masters-event.jpgwww.sussex.ac.uk/assets/images/home... https://www.sussex.ac.uk/assets/images/homepage/masters-event.jpg — 200 — 43.4 KiB — 602 ms — http/1.1https://www.sussex.ac.uk/assets/js/libs/jquery/jquery-3.6.0.min.jswww.sussex.ac.uk/assets/js/libs/jqu... https://www.sussex.ac.uk/assets/js/libs/jquery/jquery-3.6.0.min.js — 200 — 30.6 KiB — 596 ms — http/1.1https://player.vimeo.com/video/222526644?h=34e6e99d8dplayer.vimeo.com/video/222526644?h=... https://player.vimeo.com/video/222526644?h=34e6e99d8d — 200 — 11.1 KiB — 195 ms — http/1.1https://f.vimeocdn.com/p/4.46.43/js/player.module.jsf.vimeocdn.com/p/4.46.43/js/player.... https://f.vimeocdn.com/p/4.46.43/js/player.module.js — 200 — 211.3 KiB — 38 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HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100% of JavaScript execution is third-party
First-party Third-party 530ms · 9KB · £5/mo
www.sussex.ac.uk
Other
Costly
Execution 355ms
Transfer 9 KB
Monthly Cost £4/mo
Unattributable
Other
Optional
Execution 175ms
Transfer 0 KB
Monthly Cost £2/mo

These scripts may cost more than they're worth

  • www.sussex.ac.uk adds 355ms and costs ~£4/month

100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.

Learn more ▾

Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.

Source: web.dev

www.sussex.ac.uk takes 355ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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